Document Detail

Latent variable approach to the measurement of physical disability in rheumatoid arthritis.
MedLine Citation:
PMID:  15188325     Owner:  NLM     Status:  MEDLINE    
OBJECTIVE: To measure physical disability in rheumatoid arthritis (RA) using a latent variable derived from a generic and a disease-specific self-reported disability instrument and an observer-assessed functional status scale. METHODS: Consecutive patients with RA completed the modified Health Assessment Questionnaire (M-HAQ) and the Short Form 36 (SF-36) physical function scale. An observer assigned a Steinbrocker functional classification. We used principal component factor analysis to extract a latent variable from the 3 scales. We used the Bayesian Information Criterion to compare how well the new latent variable and the 3 primary scales fit the criterion standards of current work status; vital status at 6 years; grip strength; walking velocity; the timed-button test; pain; and joint tenderness, swelling, and deformity. RESULTS: Complete data were available for 776 RA patients. The extracted latent variable explained 75% of the variance in the 3 primary scales. On a scale of 0-100, higher scores representing less disability, its mean +/- SD was 56.4 +/- 22.5. Correlation between the latent variable and the M-HAQ was -0.87; between the latent variable and SF-36 physical function scale was 0.89, and between the latent variable and Steinbrocker class was -0.85. Multivariate models that included the latent variable had superior fit than did models containing the primary scales for the criteria of current working; death by 6 years; pain; joint tenderness, swelling, or deformity; grip strength; walking velocity; and timed button test. CONCLUSION: A latent variable derived from the M-HAQ, the SF-36 physical function scale, and the Steinbrocker functional class provides a parsimonious scale to measure physical disability in RA. The fit of the latent variable to comparison standards is equivalent or superior to that of the primary scales.
Agustín Escalante; Inmaculada Del Rincón; John E Cornell
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Publication Detail:
Type:  Evaluation Studies; Journal Article; Research Support, Non-U.S. Gov't; Research Support, U.S. Gov't, P.H.S.    
Journal Detail:
Title:  Arthritis and rheumatism     Volume:  51     ISSN:  0004-3591     ISO Abbreviation:  Arthritis Rheum.     Publication Date:  2004 Jun 
Date Detail:
Created Date:  2004-06-09     Completed Date:  2004-07-01     Revised Date:  2007-11-14    
Medline Journal Info:
Nlm Unique ID:  0370605     Medline TA:  Arthritis Rheum     Country:  United States    
Other Details:
Languages:  eng     Pagination:  399-407     Citation Subset:  AIM; IM    
The University of Texas Health Science Center at San Antonio, 78229-3900, USA.
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MeSH Terms
Activities of Daily Living
Aged, 80 and over
Arthritis, Rheumatoid / physiopathology*
Disability Evaluation*
Factor Analysis, Statistical
Health Status
Middle Aged
Grant Support

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine

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